This was my solution to this same issue. I found that this Nikon 90° viewfinder for a SLR camera works very well. I simply attached a half of a .965 bolt case over the threads from the viewfinder, then just slide it over my polar scope eyepiece. Definitely a improvement over kneeling on the ground.
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William Optics Zenithstar 80edll
Skywatcher quattro 8
Meade 8" sct
Meade DS-10, outreach when I eat my wheaties
Explore Scientific first light 80- outreach
Explore Scientific Exos2 PMC8 
Explore Scientific iexos100 PMC8
Canon 60d 
Nikon d90
Zwo asi120mm
Zwo asi178mc
Samsung Galaxy 7 tablet
Amazon Fire10 HD tablet
Multiple windows laptops